Alzheimer's affects around 500,000 people in the UK, accounting for 62 per cent of dementia cases.

Only 45 per cent of people with dementia in the UK currently have a diagnosis.

With the World Health Organisation forecasting that numbers of dementia sufferers will almost double worldwide every two decades, Mr Cameron said that he wants UK Government investment in dementia research to double from £66 million in 2015 to £122 million in 2025 - with similar increases from the commercial and charitable sectors.

He said that he hoped it would mark the point when "the global fight-back really started, not just in finding a cure for dementia, but also in preventing it, delaying it and, crucially, helping those with dementia to live well and with dignity."

Mr Cameron told the conference the world should be "just as resolute" in tackling dementia as it had been in the past in seeking treatments and cures for killer diseases like malaria, cancer and HIV.

“The challenge is huge and we are a long way from a cure, but there is hope,” the Prime Minister said.

“We meet with the conviction that human ingenuity can overcome the most daunting of challenges and we meet with the determination that we will take the fight to dementia and improve and save millions of lives.”

Jeremy Hunt, the Health Secretary, said that finding a cure for dementia will only be possible if people stop “sweeping it under the carpet”.

“One of the reasons I have come to the issue of dementia is because I think it's one of the last bastions of stigma in illness," Mr Hunt said. “What we do about dementia is really the litmus test for our generation of politicians.”

Mr Hunt last month disclosed a “dementia map” of England showing that in some areas of the country, fewer than four in every 10 sufferers have their condition recognised by the NHS.

“We have committed to a global plan, better support for people with dementia through research and the Prime Minister has agreed to narrow the funding gap between dementia and cancer research - something we have long campaigned for.”